The present disclosure relates to a developing device including a contact member configured to clean a sensing surface, and an image forming apparatus including the developing device.
There have been known image forming apparatuses, such as copy machines and printers, which form images on sheets by electrophotography. Such an image forming apparatus includes a developing device configured to develop an electrostatic latent image formed on an image-carrying member such as a photosensitive drum. In the developing device, toner is stored. The developing device develops the electrostatic latent image with toner to form a toner image. The toner image is transferred onto a sheet by a transfer device. The sheet, which has the toner image transferred thereon, is heated and pressed by a fixing device. The toner image is thus fixed onto the sheet. After that, the sheet, on which the toner image is fixed, is discharged from the apparatus. Thus, a series of image forming operations is completed.
Meanwhile, when the toner in the developing device is reduced because the toner has been consumed in the image forming operations, toner is additionally supplied from a toner container to the developing device. The developing device includes a toner density sensor such that toner is supplied from the toner container at appropriate times. The toner density sensor detects toner density which varies depending on the amount of remaining toner. The toner container has a sensing surface on an inner wall, and the toner density sensor detects the toner density via the sensing surface. The sensing surface is located in the toner container. Therefore, when, for example, toner adheres to the sensing surface or is accumulated near the sensing surface, the toner density sensor becomes no longer capable of accurately detecting the toner density. There has been conventionally known a developing device configured such that (i) a sensor cleaning member is provided with an agitating member configured to agitate toner and (ii) as the agitating member rotates, the sensor cleaning member makes contact with the sensing surface and slides on the sensing surface.
The developing device is configured such that a plurality of rotatable members, such as a developing roller (toner-carrying member) and the agitating member, are driven by a single driving motor. During development, the rotational force of the driving motor is transmitted via a gear to the plurality of rotatable members such as the agitating member. Thus, the plurality of rotatable members are rotated forward at a rate determined according to the gear. Meanwhile, if the developing roller or the like always rotate in one direction, time periods during which toner is accumulated may be different depending on positions in the toner container or some toner may descend and form a deposit in some positions in the toner container. In this case, a problem arises in that the toner which has been accumulated for different time periods or the toner which has formed the deposit are mixed, to cause variations in quality of toner as a whole and cause deterioration in development quality. There has been conventionally known a developing device configured such that, while no development is performed, the developing roller is rotated in the reverse direction by the driving motor so that the toner that has been accumulated or the toner that has formed the deposit is agitated and thereby variations in quality of toner can be reduced.